Q: Calculation setup for complex room geometries – How to optimize calculation speed?

A: In order to speed up point response calculations, try making a calculation at one of the most critical positions, e.g. where coupled room effects are present. (Auditorium and Combined editions only)

Before calculating the point response, set the calculation parameters in the Room Setup. Use the standard Engineering setup as a basis. Set the Impulse Response Length to a value between 2/3 and 1 times the expected Reverberation time. Set the Impulse Response Resolution to a value around 1/1000 – 1/500 of the Impulse Response Length.

Calculate the point response in the selected critical position.

Check the following in the Single Point Response (Auditorium and Combined editions only)

  1. Is the T30 calculated at all frequencies? If not, a result of 0 s appears at some frequencies. This indicates that the Impulse Response Length is not long enough; change this in the Room Setup.
  2. Compare EDT and T30. In simple, well-behaved rooms they should not differ very much; typically EDT is a little shorter than T30. However, in the case of coupled volumes and no direct sight from the receiver to the source, EDT can be longer than T30.
  3. Look at the decay curves; are they reasonably smooth? Look also at the squared impulse responses (Press A to switch from the display of integrated decays at all frequencies); the fluctuations should not have very strong spikes.
  4. Look at the Reflection Density; values between 30 and 100 / ms should normally be sufficient. If it is less than approximately 30 / ms the number of rays should be increased for reliable results.

If the quality of the results above is not satisfactory, the Room Setup should be changed as follows

  1. Increase the number of rays, (e.g. a factor of two should lead to the double reflection density).
  2. Increase the Desired late reflection density; in some cases the actually achieved density in the point response calculation may be significantly less than the desired value in the room setup.

If the quality of the results above is satisfactory, but you want to minimize the calculation time, try decreasing the number of rays and shortening the Impulse response length.

If you are in doubt whether the results are good enough or not, try to run a point response calculation using the Precision setup. In most cases this will create a very high reflection density, but in rare cases like an open air theatre the number of rays may need to be set even higher. Use the calculation results as a reference, i.e. the results obtained with the optimized setup should not deviate significantly from these results.

Grid Response calculations
For initial calculations consider using a grid with large distances between receivers or instead use Multi point responses with discrete receivers at strategic positions. Only for the final calculations make a detailed grid calculation.